This research proposes a straightforward and efficient method to optimize a sandwich monocoque car body with the developed equivalent shell element based on stiffness equivalence. The fact that stiffness rather than strength is dominant constraint for ordinary car body optimization is demonstrated. A simple but heavy flat chassis plate is utilized as upper bound, while an ideal monocoque is used as lower bound for an actual car body optimization. Convergence hours can be significantly reduced with the equivalent element and the initial-bounded method. A novel electric car body optimization is presented, fulfilling UltraLight Steel Auto Body (ULSAB) stiffness requirements and showing similar optimal weight results as a conventional approach with a much lower analysis time cost.
